CVE-2025-12421

27.11.2025, 18:15

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	NIST	9.9 CRITICAL	NETWORK	LOW	LOW	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Mattermost	CNA	9.9 CRITICAL	NETWORK	LOW	LOW	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CISA-ADP	ADP	---				---

Base Score

CVSS 3.x

EPSS Score

Percentile: 20%

Vendor	Product	Version
mattermost	mattermost_server	10.5.0 ≤ 𝑥 < 10.5.13
mattermost	mattermost_server	10.11.0 ≤ 𝑥 < 10.11.5
mattermost	mattermost_server	10.12.0 ≤ 𝑥 < 10.12.2
mattermost	mattermost_server	11.0.0 ≤ 𝑥 < 11.0.3

𝑥

= Vulnerable software versions

Common Weakness Enumeration

CWE-303 - Incorrect Implementation of Authentication Algorithm
The requirements for the software dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.

References

https://mattermost.com/security-updates